Electric lamp and similar device



Aug. 13, 1940. J. R. LAIT ET AL ELECTRIC LAMP AND S-IMILAR DEVICE FiledMay 18, 1939 Inventors James F?. Lait, Marcello Pirani,

Their` Attorney Patented Aug.'1, 1940 UNITED STATES Our inventionrelates in general to "electrio lamps and similar devices, and moreparticularly to .insulating beads or anchor members for'supk porting,and insulating from each other, a plurality of metallic wires or rods,and to their manufacture. The term wire, as used hereinafter, denotesany elongated metal body.

Insulating beads are much used for supporting' the leads or intermediatesupport wires of fila- 1'0 ments in electric incandesoent lampsand theleads or supports of electrodes in thermionic valves. Glass and ceramicmaterials are frequently used for such heads. v I It is often desirablethat the bead remain rigid 15' and retain its insulating properties attemperatures exceeding 400 C. and possibly approaching 1000 C.Accordingly; it is the object of our invention to provide beadspossessing the above properties and which are capable of being made bymass-production methods.

Further objects and advantages of our invention will appear from thefollowing description and the accompanying drawing of a` speciesthereof.

In the drawing, Figs, 1, 2 and 3 are similar sectional views through abead or anchor member comprising our invention and showing thesuccessive steps involved in the manufacture of the same; Fig. 4 is aperspective View, partly in section and on an enlarged scale, of a beador anchor member comprising our invention and useful in incandescentlamps for anchoring the ends of filament support wires; and Fig. 5 is asectional View of the bead or anchor member 35 shown in Fig. 4.

The manufacture of an insulating bead according to the invention forsupporting a plurality of wires comprises, in general, the followingsteps: (1) Forming from a ceramic material having a relatively highfusion temperature and a thermal expansion approx'mating that of thewires to be secured thereto, a body member provided with holes intowhich the wires fit, (2) filling the said holes, not 'neoessarilycompletely, 45 with glass having also a thermal expansion approximatingthat of the wires and melting at the said high temperature, and (3)forcing the ends of the wires into the said holes while the glasstherein is in a plastic state. When the product thus formed is cooleddown, the glass acts as a cement holding the wires in the holes; but ifthe wires nearly fill the holes the rigidity of the whole will dependlittle on the rigidity of the sistance between the wires will be 'thatof the ceramic material therebetvveen The holes formed in' 'step (1) maybe advantageously formed with 'a reduced inner portion, the innerportion fitting the wires closely while the outer wider portion providesspace for the cementing glass. "The term "fit, however, does notnecessarily imply thatthe wire is to' be held in 'the holes withouttheuseof cementing glass. Further, in order that the cementing glasscompletely fill'the holes, it ispreferable to provide the inneror'reducedportions of the holes with side passages leading to thesurface of the block, through which airmay escape when the glass isintroduced 'into the holes. In step (2) the ceramic may be heated to atemperature above the meltng point of th'e glass 'Whereupon rods ofglass of appropriate diameter may be introduced into the holes andwithdrawn again when the necessary quantity of glass has melted ofi fromtheir ends. steps (2) and (3) can therefore readily be performed onmachines similar to the well-known machines for inserting pig-tails intothe stern of an incandescent lamp. Other procedures, however, arepossible. Thus in step (2), the glass may be inserted as pieces of rodinto the holes in the ceramic body while the latter is at roomtemperature, and the ceramic body then heated so as to melt the glass.

The thermai expansions of the ceramic body,

the cementing glass, and the wires to be supported thereby are deemed tobe approximately the same if the final structure is not liable to crackunder the changes of temperature to which it is exposed.

Where the wires to be supported are of molybdenum, a suitable ceramic isone having the following composition: Al2O3-64 per cent, SiO2-25 percent, BeO--7 per cent, Mg--2 per cent, ThOz-Z per cent. The expansion ofthis material is about x 10- per C. Likewise, a suitable cementing glassis one having the following composition: SiO2-54.7 per cent,(Al2O3+Fe2O3)-- 20.9 per cent, Cao- .7 per cent, B2O3- .7 per cent,Bac-3.0 per cent. The expansion coefficient of this .glass is about 4.6x 10- per C.

Steatite may be used as the ceramic. In this case, the wires may then beof nickel-iron having a similar eXpansion.

Referring to the drawing, the insulating bead or anchor member shown inFigs. 1-3 comprises a ceramic body I of the aforesaid composition andprovided with a plurality of holes Z each having a reduced inner portion3 terminating within the ceramic body. The ceramic body l is furtherprovided with a plurality of side passages or holes 6, adjacent theinner end of the holes 2 and leading to the surface of said ceramicbody, there being a side passage 6 for each of the holes 2. Wires 4 ofmolybdenum extend into the holes 2, the said wires being of such size asto have a sliding fit within the reduced inner portion 3 of the holes.Securing each wire 4 within its respective hole 2 is a quantity ofcementing glass 5 of the above referred to composition.

Fig. 1 illustrates the ceramic body formed by step (1), while Fig. 2shows the said body after step (2), in which the body is heated to atemperature above the melting point of the cementing glass 5 and rods ofthe said glass inserted into the holes and allowed to melt down so as tocompletely fill the reduced inner portions 3 of the holes 2 and, ifdesired, a part of the side passages 6 as well. Fig. 3 illustrates thecompleted bead according to' our invention after step (3), in which thewires are inserted into the holes 2 while the cementing glass 5 is stillin a plastic state and the entire structure then allowed to cool down toroom temperature. In this iatter step, part of the excess glass islikely to emerge at the outer ends of the side passages 6 when the wires4 are inserted into the holes 2. Figs. 4 and 5 illustrate the inventionas it might be applied to an incandescent lamp wherein the ceramic beadI' is secured to a support or arbor wire 'I the opposite end of which issecured to the lamp stern (not shown) in well-known manner. A pluralityof filament-supporting anchor wires 4' have their ends secured withinthe holes 2', 3' by fused glass 5' in the manner described above inconnection with Figs. 1-3. The filament (not shown) is supported byhooks or loops in the ends of said wires 4' and is arranged thereon inthe form of an arc or horseshoe, as is well known.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An anchor member comprising a body of ceramic material having aplurality of holes therein terminating within said body and sidepassages extending laterally from a point adjacent the inner ends ofsaid holes to a surface of said body, a support wire extending into eachof said holes, and a quantity of fused vitreous material securing eachof said wires in its hole and extending into the passage leading fromsaid hole.

2. An anchor member comprising a body of ceramic material having aplurality of holes therein terminating within said body, a support wireextending into each of said holes, the inner ends of said holes being ofreduced diameter to fit said wires c1ose1y,- and a quantity of fusedvitreous material securing each of said wires in its hole.

3. An anchor member comprsing a body of ceramic material having aplurality of holes therein terminating within said body, a support wireextending into each of said holes, the inner ends of said holes being ofreduced diameter to fit said wires closely and having side passagescommunicating therewith and extending laterally therefrom to a surfaceof said body, and a quantity of fused vitreous material securing each ofsaid wires ir its hole and extending into the passage leading from saidhole.

JAMES R. LAIT. MARCELLO PIR/ANI.

